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Old 07-27-2013, 03:40 PM   #1
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Quote:
Originally Posted by Brad Roberts View Post
Stop and go traffic kills the IMS bearing (after the grease leaves the bearing)

The constant in and out of the variocam on the passenger side of the engine stresses the IMSB.

Variocam comes in between 2850-3000 rpm. If you drive above this or below this, you have less chance of failure (we see no failures in the race cars as we are constantly above 3krpm)

People in LA going from zero to 40 to zero to 40 to zero to 40 in 1st gear, stress the IMSB BIG time. Each time the chain gets loaded in the 2850-3000 rpm.
Gotta be honest Brad, I can't see that being a major factor in reality.

I'm not disputing the engineering argument. But very frequent transition past that rev range will be normal for the vast, vast majority of road-going Boxsters. And the vast majority of that vast majority doesn't suffer IMS bearing failure. So it can't be that critical.
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Old 07-27-2013, 04:51 PM   #2
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No worries!!

The majority of our highways are 65-70 MPH. In most stock Boxster's with stock size tires, this means 2800-3000 is 65-75mph.

As you speed up and slow down between 2800-3000 it kicks in and out. Unless you set the cruise control at 3100. *most* drivers are pedaling the car between 2800-3000 rpm constantly loading and unloading the chain from the IMSB and passenger side cams.

Each and every failure, I speak with the owner and ask them about their driving habits. I don't say anything about what I think, I ask them about their commute to work and weekend habits.

What "I've" found.. the people who haul ass with little to no traffic have a lot less problems than those who "cruise" the legal speed limit and sit in a lot of traffic every morning and evening while commuting.

We have disassembled a LOT of failed engines, and built a LOT of engines. Some are raced, some are in commuter cars.

It's just my opinion If others choose not to believe it? so be it. No loss on my part. I know how I drive them, and I know what I say to my customers about their driving habits.
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